A search engine is a type of software system designed to allow users to find information stored on the World Wide Web by processing keywords or phrases. Functionally, the system operates through a three-part mechanism: crawling, indexing, and querying. Crawling involves automated programs systematically navigating the web to discover new and updated content. The collected data is then processed and stored in an index, a massive, structured database that maps keywords to specific web locations, much like a comprehensive library catalog. When a user enters a query, the engine performs a matching algorithm against this index, retrieving potential sources and presenting them as a ranked list of results intended to maximize relevance and utility to the user.